For example, Patent Document 1 (Japanese Patent Application Publication No. 2014-187073) discloses a semiconductor device, including a first insulating film formed on a major surface of a semiconductor substrate, an electrode pad formed on the first insulating film and constituted of an alloy film with Cu added, a second insulating film formed on the major surface of the semiconductor substrate so as to cover a portion of an upper surface of the electrode pad, a first opening portion formed in the second insulating film and exposing a portion of the upper surface of the electrode pad, a plating film electrically connected to the electrode pad via the first opening portion, and a plating adhesion film formed on an upper surface of the plating film, and with which a concentration of the Cu added to the alloy film constituting the electrode pad is not less than 2 wt %. In the semiconductor device, the plating film is formed by an electroless plating method.